Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$53.57	9.487%	$58.6522	$58.65	$58.65	$58.70
Purchase #2	$231.67	10.429%	$255.8309	$255.83	$255.85	$255.80
Purchase #3	$41.33	11.634%	$46.1383	$46.14	$46.15	$46.10
Purchase #4	$98.75	10.587%	$109.2047	$109.20	$109.20	$109.20
Purchase #5	$96.68	3.322%	$99.8917	$99.89	$99.90	$99.90
Purchase #6	$93.73	7.390%	$100.6566	$100.66	$100.65	$100.70
Purchase #7	$39.96	5.461%	$42.1422	$42.14	$42.15	$42.10
7 purchase totals =	$655.69		$712.5166	$712.51	$712.55	$712.50